§1036.231 Powertrain Families.

(a) If you choose to perform powertrain testing as specified in §1036.545, use good engineering judgment to divide your product line into powertrain families that are expected to have similar criteria emissions throughout the useful life as described in this section. Your powertrain family is limited to a single model year.

(b) Except as specified in paragraph (c) of this section, group powertrains in the same powertrain family if they share all the following attributes:

(1) Have the same engine design aspects as specified in §1036.230.

(2) [Reserved]

(3) Number of clutches.

(4) Type of clutch ( e.g., wet or dry).

(5) Presence and location of a fluid coupling such as a torque converter.

(6) Gear configuration, as follows:

(i) Planetary ( e.g., simple, compound, meshed-planet, stepped-planet, multi-stage).

(ii) Countershaft ( e.g., single, double, triple).

(iii) Continuously variable ( e.g., pulley, magnetic, toroidal).

(7) Number of available forward gears, and transmission gear ratio for each available forward gear, if applicable. Count forward gears as being available only if the vehicle has the hardware and software to allow operation in those gears.

(8) Transmission oil sump configuration ( e.g., conventional or dry).

(9) The power transfer configuration of any hybrid technology ( e.g., series or parallel).

(10) The type of any RESS ( e.g., hydraulic accumulator, Lithium-ion battery pack, ultracapacitor bank).

(c) For powertrains that share all the attributes described in paragraph (b) of this section, divide them further into separate powertrain families based on common calibration attributes. Group powertrains in the same powertrain family to the extent that powertrain test results and corresponding emission levels are expected to be similar throughout the useful life.

(d) You may subdivide a group of powertrains with shared attributes under paragraph (b) of this section into different powertrain families.

(e) In unusual circumstances, you may group powertrains into the same powertrain family even if they do not have shared attributes under in paragraph (b) of this section if you show that their emission characteristics throughout the useful life will be similar.

(f) If you include the axle when performing powertrain testing for the family, you must limit the family to include only those axles represented by the test results. You may include multiple axle ratios in the family if you test with the axle expected to produce the highest emission results.

[91 FR 7778, Feb. 18, 2026]